Over the years, many kinds of leg prostheses have been devised in effort to replace the leg or legs that amputees have lost. All these leg prostheses have the difficult task of giving to these amputees a life as normal as possible. The complexity of human locomotion, however, is such that conventional leg prostheses have until now only been using passive mechanisms in the most sophisticated available devices. Conventional leg prostheses are very limited compared to a real human leg and some needs were thus not entirely fulfilled by them.
According to amputees, specific conditions of use of conventional leg prostheses, such as repetitive movements and continuous loading, typically entail problems such as increases in metabolic energy expenditures, increases of socket pressure, limitations of locomotion speeds, discrepancies in the locomotion movements, disruptions of postural balance, disruptions of the pelvis-spinal column alignment, and increases in the use of postural clinical rehabilitation programs.
Another problem is that during the amputees' locomotion, energy used for moving the prosthesis mainly originates from the amputees themselves because conventional leg prostheses do not have self-propulsion capabilities. This has considerable short and long-term negative side effects. Recent developments in the field of energy-saving prosthetic components have partially contributed to improve energy transfer between the amputees and their prosthesis. Nevertheless, the problem of energy expenditure is still not fully resolved and remains a major concern.
A further problem is that the dynamic role played by the stump during the amputees' locomotion renders difficult the prolonged wearing of conventional leg prostheses. This may create, among other things, skin problems such as folliculitis, contact dermatitis, oedema, cysts, skin shearing, scarring and ulcers. Although these skin problems may be partially alleviated by using a silicon sheath, a complete suction socket or powder, minimizing these skin problems remain a concern.
Considering this background, it clearly appears that there was a need to develop improved leg prosthesis for above-knee amputees.